1. Field of the Invention
The present invention relates to an electric power steering apparatus for a vehicle and, more particularly, relates to an electric power steering apparatus in which reliability thereof is improved by enhancing the heat radiation performance of a motor control device which controls a motor and size reduction thereof is achieved.
2. Description of the Related Art
Generally, an electric power steering apparatus mounted on a vehicle is designed so that, when a driver performs a steering operation, a torque sensor detects a steering torque produced on a steering shaft, and a motor control device controls a motor based on the detected torque value in order to assist in the steering.
Recently, such an electric power steering apparatus has been widely used, being mounted on compact cars and midsize cars in addition to light cars. Mainly, the motor and the motor control device are individually mounted on separated positions away from each other outside and inside a vehicle compartment, respectively. Thus, a long wiring harness is used to provide electric connection between the motor and the motor control device. The adoption of the long wiring harness causes various problems such as power loss due to wiring resistance, noise emission by the apparatus while the motor is being driven, and increases in the number of components.
As an example of an electric power steering apparatus in view of the above problems, there has been proposed an electric power steering apparatus including a motor accommodated in a housing, and a control circuit unit accommodated in a casing, in which the housing is disposed adjacently to the casing, and in which the motor is connected by a bus bar to the control circuit unit, whereby the motor and the control circuit unit are made into an integral structure (see JP Patent Publication (Kokai) No. 2003-204654 A).
Also proposed is, in addition to the above example, an electric power steering apparatus including a control device accommodated in the space defined by a housing and a cover of the housing, and an electric motor which is controlled by the control device, in which motor terminals each projecting from an opening of the cover for the control device is electrically connected within the electric motor (see JP Patent Publication (Kokai) No. 2003-267233 A).